Novel pituitary transcription factors, Prrx 1 and Prrx2, may be involved in the pituitary organogenesis under differential gene regulation by several transcription factors

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: MON 112-141-Hypothalamus-Pituitary Development & Biology
Basic/Clinical
Monday, June 17, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board MON-119
Hiroki Ueharu*, Shiori Shibuya, Mitsuyoshi Tsuda, Masayo Sekita, Masashi Higuchi, Saishu Yoshida, Hideji Yako, Naoko Kanno, Mo Chen, Takako Kato and Yukio Kato
Meiji University, Kawasaki, Kanagawa, Japan
Molecular mechanism of the pituitary organogenesis is still under investigation as an important issue of the pituitary gland. Recently, we have identified that paired related homeobox 1 and 2 (Prrx1andPrrx2), which are involved in osteogenesis of bone, inner ear and limb, are expressed in the pituitary and participate in the function of stem/progenitor cells and vasculogenesis. Hence, we aimed to clarify a regulatory mechanism of expression of the Prrx1 and Prrx2.

Reporter vectors and the truncated mutants were constructed by ligating the 5'-upstream of both genes (Prrx1; 2.3 kb and Prrx2; 5.1 kb) into the pSEAP2-Basic vector containing the secreted alkaline phosphatase gene as a reporter molecule and expression vectors of transcription factors were constructed in the pcDNA3.1zeo. Reporter assay was performed using cell lines of CHO (derived from ovary) and NIH3T3 (derived from fibroblast and expresses Prrx1 and Prrx2).

Reporter assay showed that the proximal region of Prrx1 (-450/+103) and Prrx2 (-372/+21) are positive activity in NIH3T3 but not in CHO. Cotransfection of CHO with expression vectors harboring cDNAs (Hey1Hey2Foxj1Pax6, and Klf6) demonstrated that Pax6, a regulator for development and differentiation of the pituitary, activated the expression of both promoters and Klf6, a regulator for proliferation and apoptosis, activated only Prrx2. In contrast, Foxj1, an important factor of cilia formation, repressed both promoter activities in CHO and NIH3T3. Notably, Hey1 and Hey2, factors for maintenance of an undifferentiated state, repressed the promoter activity of Prrx2 but not Prrx1 in both cell lines.

More recently, using newly generated specific antibodies each for PRRX1 and PRRX2, we have demonstrated that, in the rat pituitary, PRRX1 is present stem/progenitor cells at embryonic and postnatal stage and PRRX2 is present in stem cells at only postnatal stage. Furthermore, we found that Prrx1 and Prrx2 are involved in vasculogenesis during embryonic development, indicating that different temporospatial expression of Prrx1 and Prrx2 plays crucial roles in pituitary organogenesis. The present results that several transcription factors regulate Prrx1 and Prrx2 with specific or common effects by activation or repression in two cell lines provide interesting insight to understand the function of both factors during the pituitary organogenesis.

Nothing to Disclose: HU, SS, MT, MS, MH, SY, HY, NK, MC, TK, YK

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